CuteMouse is a DOS based mouse driver, fully written in assembly language. It's optimized for size (and speed) to allocate as small as possible amount of your precious 640KB RAM. It currently supports serial and PS/2 mice and, if BIOS support present an
an ethernet-based file system for DOS
EtherDFS is an 'installable filesystem' TSR for DOS. It maps a drive from a remote computer (typically Linux-based) to a local drive letter, using raw ethernet frames to communicate. For years, I was using LapLink to transfer files between my various "retro" computers. It works, yes, but it's also annoyingly slow and requires constant attention. One day I thought, "Wouldn't it be amazing if all my PCs could share a common network drive, similarly to how NFS operates in the *nix world?". This day EtherDFS was born. I clearly didn't invent anything - the concept has been around almost as long as the first IBM PC, and several commercial products addressed that need in the past. I am not aware, however, of any free and open-source solution.